1. Field of the Invention
This invention relates to motor-operated fuel pumps adapted for use in automobiles, trucks and the like and particularly relates to the incorporation of an electrical filter into the pump motor electric circuit to eliminate or minimize radio frequency interferences that can otherwise be generated while the fuel pump motor is in operation.
2. Description of Prior Developments
Fuel pump motors sometimes produce undesired frequency signals that can interfere with the operation of radios and computers on board a vehicle. The undesired signals can be due to small electrical arcs associated with movements of the motor brushes across the commutators. As the brush approaches or recedes from a commutator surface the electrical voltage tends to leap across the brush-commutator space to generate an electrical arc. There is thus superimposed on the steady state current a series of electrical spikes or surges related to the motor-operating frequency. The superimposed high frequency signal can interfere with other equipment on board the vehicle, especially radios and computers.
It is known that a high frequency signal can be eliminated or minimized by use of a filter circuit which includes a capacitance and an inductance. The filter is designed to offer a high impedance to the undesired frequency while offering minimal impedance to the steady state low frequency signal. The inductance provides the high impedance, and the capacitor shunts the high frequency signal to ground. Applicable filter circuits are mentioned in U.S. Pat. No. 2,308,013 to Lee, U.S. Pat. No. 4,079,435 to Brown, U.S. Pat. No. 4,080,552 to Brown, and U.S. Pat. No. 4,554,608 to Block.